Add warning when CUDA is not available

[jcelerier]

And add support for installing CUDA like we do with Koaia

[samamou]

check system.availableCudaDevice() https://github.com/ossia/score/blob/30384e3a5cbaf9fed7958ce8f318e5dd106eb15a/src/plugins/score-plugin-js/JS/Qml/Utils.cpp#L257